The axle housings of vehicles used for earth moving, construction, material handling, mining, and the like, are partially filled with oil or other lubricating fluid (collectively, “oil”) to facilitate contact between meshing gears contained in the housing. It is desirable to have a film of oil between meshing gear teeth in order to avoid the extreme heat that may otherwise be created in the contact area of the teeth. Such extreme heat causes, between the surfaces of the meshing gear teeth, micro-welding that results in tearing and pitting of the gear teeth and breaking of the teeth due to material fatigue.
Each axle housing typically contains a toothed gear set such as a ring gear and a pinion gear. The teeth of the smaller dimensioned pinion gear mesh with the teeth of the ring gear. Generally, an output shaft from the vehicle transmission provides power to rotate the pinion gear. The rotating and meshing of the pinion gear teeth with the ring gear teeth drives the ring gear and transfers power, through the rotating ring gear, to the wheels of the vehicle. The gear ratio of the pinion gear to the ring gear typically creates a reduction of the input speed from the transmission and an increase in the torque applied to the wheels.
Generally, the axle housing is filled with enough oil to ensure that all gear teeth, including those of the ring and pinion gears, are lubricated. Thus, a larger gear disposed generally vertically within the axle housing (such as the ring gear), which requires a lower fill level of oil in the axle housing, has to rotate through a much deeper oil fill level in order to ensure that other gears (for example, those with smaller diameters, those positioned horizontally) are adequately lubricated. Thus, the oil flow around a large gear, such as the ring gear, is often turbulent due to the depth of oil in which the gear must rotate. This turbulence may be compounded by the meshing of gears, such as the ring and pinion gears, that have different rotational axes. The input power required to overcome the resistance of the oil to the rotation of the gear(s) may be referred to as “churning loss.” This churning loss results in increased fuel usage as more input power must be applied to make-up for the churning loss.
U.S. Publication No. 2010/0009800 (“Altvaten et al.”) published Jan. 14, 2010 is an example of prior art related to oil flow associated with ring gears in axle drives. FIG. 1 of Altvaten et al. illustrates the flow of oil in an axle drive provided by rotation of a ring gear. According to Altvaten et al., movement of the oil by the ring gear creates turbulence that sprays the oil over the differential cage and reduces the useful quantity of oil delivered for circulation by the ring gear. FIG. 2 of Altvaten et al. illustrates an annular disk positioned between the ring gear and the differential cage. The disk forms a seal against the differential cover and provides a barrier that redirects the sprayed oil back to the ring gear. While this design may maximize the volume of oil recirculated around the ring gear, it disadvantageously increases churning loss because an increase in the volume of oil around the ring gear creates more turbulence and drag on the ring gear.
U.S. Pat. No. 5,505,112 issued Apr. 9, 1996 (the '112 Patent) incorporates a semi-circle half shield in a countershaft assembly having multiple gears of various diameters disposed along a common axis. As shown in FIGS. 2-3 of the '112 Patent, the shield isolates the gear with the largest radius in a separate reservoir from the other smaller gears positioned along a common axis of rotation. This type of half shield has drawbacks and may not be effective when utilized with meshing gears having different axes of rotation, particularly meshing ring and pinion gear sets where the pinion may rotate around an axis of rotation that is generally perpendicular to the axis of rotation for the ring gear. A better design is needed that decreases churning loss.